Verdict still out on prostate test
Friday, July 06, 2007
by JIM RITTER Health Reporter
Dave Bigg was in such good health he hadn't seen a doctor in 20 years.
But after Bigg finally underwent a routine physical, he learned he had a suspicious score on a PSA prostate cancer screening test.
Bigg later underwent surgery at Northwestern Memorial Hospital to remove his cancerous prostate.
"Thank God for the PSA test," he said. "This saved me a world of trouble."
Cook County Board President Todd Stroger had a similar experience. "I want to say one thing, above all others, to men," Stroger said. "Take the test."
The American Cancer Society recommends that men who have at least a 10-year life expectancy be offered PSA tests yearly after age 50, along with a gloved finger exam. Those at higher risk, including African Americans and men with family histories, should be offered the tests as early as age 40.
PSA tests have been in use for more than 20 years, and more than half of men over age 50 have had one in the past year. Nevertheless, the PSA remains one of the most controversial screening tests in medicine.
Skeptics say the test is often inaccurate and can lead to needless anxiety or unnecessary treatments that can cause impotence or incontinence.
The U.S. Preventive Services Task Force said there isn't enough evidence to recommend either for or against routine PSA testing.
While PSA tests can detect some cancers when they are in early, curable stages, it's unclear whether the overall benefits outweigh the potential harms, the task force said.
Prostate cancer is the second most common cancer in men, and will kill about 27,000 Americans this year.
Specialists who treat prostate cancer tend to be bigger advocates of PSA tests than primary care doctors, said Northwestern Memorial urologist Dr. William Catalona, a leading PSA proponent.
Given the conflicting opinions, what should men do? University of Chicago internist Dr. David Meltzer suggests doctors and patients discuss the pros and cons of PSA tests and then decide together what to do.
That may sound pretty complicated. "But the most dangerous thing we can do in prostate cancer is to resort to simple rules," Meltzer said.
The prostate is the size of a chestnut and weighs two-thirds of an ounce. The gland secretes a milky fluid that helps transport sperm.
PSA stands for prostate specific antigen, a protein produced in the prostate. The test requires a simple blood sample, and costs $50 to $100. Insurance usually covers the test.
PSA testing may explain why there's been a 32.5 percent decrease in the prostate cancer death rate since 1995, Catalona said. But PSA skeptics say this might be due to improved treatments.
Catalona offers two other statistics favoring PSA tests: Before 1990, 20 percent of prostate cancers were diagnosed in late stages after the cancer had spread. Today, it's only 5 percent. Also, the five-year survival rate has increased from 75 percent in 1991 to 99 percent today.
Still, there are serious drawbacks:
• False positives. Conditions other than cancer, such as enlarged or inflamed prostates, can also raise PSA levels. In 70 percent to 75 percent of cases, biopsies show there was no cancer. In addition to causing needless anxiety, biopsies can cause bleeding or infections.
• False negatives. Sometimes, patients with normal PSA levels actually have cancer, leading to a false sense of security.
• PSA readings below 4.0 once were considered normal. Many doctors have lowered the cutoff to 2.5. Also, how fast PSA levels have increased over time can be more important than a single reading. So if you get annual PSA tests, keep records of each test.
• Over-diagnosis. Prostate cancer usually grows very slowly. A PSA test could detect a small cancer that might not be life-threatening, subjecting a patient to unnecessary surgery or radiation.
• Too late. In some cases, cancers detected by PSA tests are so aggressive they have already spread, so the PSA detection comes too late to do much good.
Two large studies underway may finally determine whether PSA tests do more good than harm, said Dr. Ned Calonge, chairman of the Preventive Services Task Force.
Participants were randomly assigned to either receive PSA tests or not get screened. They will be followed for years, and researchers will see which group fares better.
Initial findings are due in a few years. But the results still might not settle the debate, Catalona said, because the studies have serious design flaws.